Multi-layer spherical head model for EEG forward computation. More...

#include <fwd_eeg_sphere_model.h>

Public Types
typedef std::unique_ptr< FwdEegSphereModel >	UPtr

Public Member Functions
	FwdEegSphereModel ()
	FwdEegSphereModel (const FwdEegSphereModel &p_FwdEegSphereModel)
virtual	~FwdEegSphereModel ()
double	fwd_eeg_get_multi_sphere_model_coeff (int n)
bool	fwd_setup_eeg_sphere_model (float rad, bool fit_berg_scherg, int nfit)
bool	fwd_eeg_fit_berg_scherg (int nterms, int nfit, float &rv)
int	nlayer () const

Static Public Member Functions
static FwdEegSphereModel::UPtr	fwd_create_eeg_sphere_model (const QString &name, int nlayer, const Eigen::VectorXf &rads, const Eigen::VectorXf &sigmas)
static FwdEegSphereModel::UPtr	setup_eeg_sphere_model (const QString &eeg_model_file, QString eeg_model_name, float eeg_sphere_rad)
static fitUser	new_fit_user (int nfit, int nterms)
static void	next_legen (int n, double x, double &p0, double &p01, double &p1, double &p11)
static void	calc_pot_components (double beta, double cgamma, double &Vrp, double &Vtp, const Eigen::VectorXd &fn, int nterms)
static int	fwd_eeg_multi_spherepot (const Eigen::Vector3f &rd, const Eigen::Vector3f &Q, const Eigen::Matrix< float, Eigen::Dynamic, 3, Eigen::RowMajor > &el, int neeg, Eigen::VectorXf &Vval, void *client)
static int	fwd_eeg_multi_spherepot_coil1 (const Eigen::Vector3f &rd, const Eigen::Vector3f &Q, FwdCoilSet &els, Eigen::Ref< Eigen::VectorXf > Vval, void *client)
static bool	fwd_eeg_spherepot_vec (const Eigen::Vector3f &rd, const Eigen::Matrix< float, Eigen::Dynamic, 3, Eigen::RowMajor > &el, int neeg, Eigen::MatrixXf &Vval_vec, void *client)
static int	fwd_eeg_spherepot_coil_vec (const Eigen::Vector3f &rd, FwdCoilSet &els, Eigen::Ref< Eigen::MatrixXf > Vval_vec, void *client)
static int	fwd_eeg_spherepot_grad_coil (const Eigen::Vector3f &rd, const Eigen::Vector3f &Q, FwdCoilSet &coils, Eigen::Ref< Eigen::VectorXf > Vval, Eigen::Ref< Eigen::VectorXf > xgrad, Eigen::Ref< Eigen::VectorXf > ygrad, Eigen::Ref< Eigen::VectorXf > zgrad, void *client)
static int	fwd_eeg_spherepot (const Eigen::Vector3f &rd, const Eigen::Vector3f &Q, const Eigen::Matrix< float, Eigen::Dynamic, 3, Eigen::RowMajor > &el, int neeg, Eigen::VectorXf &Vval, void *client)
static int	fwd_eeg_spherepot_coil (const Eigen::Vector3f &rd, const Eigen::Vector3f &Q, FwdCoilSet &els, Eigen::Ref< Eigen::VectorXf > Vval, void *client)
static void	compose_linear_fitting_data (const Eigen::VectorXd &mu, fitUser u)
static double	compute_linear_parameters (const Eigen::VectorXd &mu, Eigen::VectorXd &lambda, fitUser u)
static double	one_step (const Eigen::VectorXd &mu, const void *user_data)

Public Attributes
QString	name
std::vector< FwdEegSphereLayer >	layers
Eigen::Vector3f	r0
Eigen::VectorXd	fn
int	nterms
Eigen::VectorXf	mu
Eigen::VectorXf	lambda
int	nfit
int	scale_pos

Detailed Description

Multi-layer spherical head model for EEG forward computation.

Implements FwdEegSphereModel (Replaces *fwdEegSphereModel,fwdEegSphereModelRec struct of MNE-C fwd_types.h).

Definition at line 96 of file fwd_eeg_sphere_model.h.

Member Typedef Documentation

◆ UPtr

typedef std::unique_ptr<FwdEegSphereModel> FWDLIB::FwdEegSphereModel::UPtr

Unique pointer type for FwdEegSphereModel.

Definition at line 99 of file fwd_eeg_sphere_model.h.

Constructor & Destructor Documentation

◆ FwdEegSphereModel() [1/2]

FwdEegSphereModel::FwdEegSphereModel ( )

explicit

Constructs the Forward EEG Sphere Model

Definition at line 78 of file fwd_eeg_sphere_model.cpp.

◆ FwdEegSphereModel() [2/2]

FwdEegSphereModel::FwdEegSphereModel ( const FwdEegSphereModel & p_FwdEegSphereModel )

explicit

Copy constructor.

Parameters

[in] p_FwdEegSphereModel Forward EEG Sphere Model which should be copied.

Definition at line 88 of file fwd_eeg_sphere_model.cpp.

◆ ~FwdEegSphereModel()

FwdEegSphereModel::~FwdEegSphereModel ( )

virtual

Destroys the Electric Current Dipole description

Definition at line 156 of file fwd_eeg_sphere_model.cpp.

Member Function Documentation

◆ calc_pot_components()

void FwdEegSphereModel::calc_pot_components	(	double	beta,
		double	cgamma,
		double &	Vrp,
		double &	Vtp,
		const Eigen::VectorXd &	fn,
		int	nterms )

static

Calculate the radial and tangential potential components for a dipole in a layered sphere model using a Legendre polynomial series expansion.

Parameters

[in]	beta	Ratio of dipole distance to field point distance.
[in]	cgamma	Cosine of the angle between dipole and field point vectors.
[out]	Vrp	Radial component of the potential.
[out]	Vtp	Tangential component of the potential.
[in]	fn	Pre-computed expansion coefficients.
[in]	nterms	Maximum number of terms in the series.

Definition at line 344 of file fwd_eeg_sphere_model.cpp.

◆ compose_linear_fitting_data()

void FwdEegSphereModel::compose_linear_fitting_data	(	const Eigen::VectorXd &	mu,
		fitUser	u )

static

Build the data matrix and target vector for the linear part of the Berg-Scherg parameter fit.

Parameters

[in]	mu	Distance multipliers for the equivalent dipoles.
[in]	u	Fitting workspace (M and y are populated on output).

Definition at line 949 of file fwd_eeg_sphere_model.cpp.

◆ compute_linear_parameters()

double FwdEegSphereModel::compute_linear_parameters	(	const Eigen::VectorXd &	mu,
		Eigen::VectorXd &	lambda,
		fitUser	u )

static

Solve for the optimal lambda (dipole magnitude) parameters given fixed mu values using SVD. Returns the relative variance goodness-of-fit metric.

Parameters

[in]	mu	Distance multipliers for the equivalent dipoles.
[out]	lambda	Computed dipole magnitudes.
[in]	u	Fitting workspace.

Returns: Relative variance (0 = perfect fit, 1 = no fit).

Definition at line 967 of file fwd_eeg_sphere_model.cpp.

◆ fwd_create_eeg_sphere_model()

FwdEegSphereModel::UPtr FwdEegSphereModel::fwd_create_eeg_sphere_model	(	const QString &	name,
		int	nlayer,
		const Eigen::VectorXf &	rads,
		const Eigen::VectorXf &	sigmas )

static

Create a new multi-layer EEG sphere model structure.

Sorts layers by radius and scales radii relative to the outermost layer.

Parameters

[in]	name	Textual identifier for the model.
[in]	nlayer	Number of concentric spherical layers.
[in]	rads	Radius values for each layer.
[in]	sigmas	Conductivity values for each layer.

Returns: Pointer to the newly created sphere model.

Definition at line 119 of file fwd_eeg_sphere_model.cpp.

◆ fwd_eeg_fit_berg_scherg()

bool FwdEegSphereModel::fwd_eeg_fit_berg_scherg	(	int	nterms,
		int	nfit,
		float &	rv )

Fit Berg-Scherg equivalent spherical model parameters (mu and lambda) by minimizing the difference between actual and approximated series expansions using simplex optimization.

On success, updates the internal mu and lambda member vectors.

Parameters

[in]	nterms	Number of terms in the series expansion.
[in]	nfit	Number of equivalent dipoles to fit (must be >= 2).
[out]	rv	Relative variance of the final fit.

Returns: true if fitting succeeded, false otherwise. Number of layers.

Definition at line 1046 of file fwd_eeg_sphere_model.cpp.

◆ fwd_eeg_get_multi_sphere_model_coeff()

double FwdEegSphereModel::fwd_eeg_get_multi_sphere_model_coeff ( int n )

fwd_multi_spherepot.c Get the model depended weighting factor for n

Parameters

[in] n coefficient to which the expansion shopuld be calculated.

Returns: the weighting factor for n.

Definition at line 205 of file fwd_eeg_sphere_model.cpp.

◆ fwd_eeg_multi_spherepot()

int FwdEegSphereModel::fwd_eeg_multi_spherepot	(	const Eigen::Vector3f &	rd,
		const Eigen::Vector3f &	Q,
		const Eigen::Matrix< float, Eigen::Dynamic, 3, Eigen::RowMajor > &	el,
		int	neeg,
		Eigen::VectorXf &	Vval,
		void *	client )

static

Compute EEG potentials at multiple electrodes for a current dipole in a multi-layer spherical head model.

Based on the formulas in Zhang (1995) and Mosher et al. (1996).

Parameters

[in]	rd	Dipole position.
[in]	Q	Dipole moment.
[in]	el	Electrode positions (neeg x 3).
[in]	neeg	Number of electrodes.
[out]	Vval	Computed potential values at each electrode.
[in]	client	Pointer to the FwdEegSphereModel.

Returns: OK on success, FAIL otherwise.

Definition at line 371 of file fwd_eeg_sphere_model.cpp.

◆ fwd_eeg_multi_spherepot_coil1()

int FwdEegSphereModel::fwd_eeg_multi_spherepot_coil1	(	const Eigen::Vector3f &	rd,
		const Eigen::Vector3f &	Q,
		FwdCoilSet &	els,
		Eigen::Ref< Eigen::VectorXf >	Vval,
		void *	client )

static

Calculate EEG potentials at compound electrodes (coils) by summing weighted contributions from individual integration points.

Parameters

[in]	rd	Dipole position.
[in]	Q	Dipole moment.
[in]	els	Set of coils/electrodes.
[out]	Vval	Computed potentials (one per coil).
[in]	client	Pointer to the FwdEegSphereModel.

Returns: OK on success, FAIL otherwise.

Definition at line 496 of file fwd_eeg_sphere_model.cpp.

◆ fwd_eeg_spherepot()

int FwdEegSphereModel::fwd_eeg_spherepot	(	const Eigen::Vector3f &	rd,
		const Eigen::Vector3f &	Q,
		const Eigen::Matrix< float, Eigen::Dynamic, 3, Eigen::RowMajor > &	el,
		int	neeg,
		Eigen::VectorXf &	Vval,
		void *	client )

static

fwd_multi_spherepot.c

This routine calculates the potentials for a specific dipole direction

This routine uses the acceleration with help of equivalent sources in the homogeneous sphere.

Parameters

[in]	rd	Dipole position.
[in]	Q	Dipole moment.
[in]	el	Electrode positions.
[in]	neeg	Number of electrodes.
[in]	Vval	The potential values.
[in]	client.

Returns: true when successful.

Definition at line 699 of file fwd_eeg_sphere_model.cpp.

◆ fwd_eeg_spherepot_coil()

int FwdEegSphereModel::fwd_eeg_spherepot_coil	(	const Eigen::Vector3f &	rd,
		const Eigen::Vector3f &	Q,
		FwdCoilSet &	els,
		Eigen::Ref< Eigen::VectorXf >	Vval,
		void *	client )

static

fwd_multi_spherepot.c

Calculate the EEG in the sphere model using the megCoil structure MEG channels are skipped

Parameters

[in]	rd	Dipole position.
[in]	Q	Dipole moment.
[in]	els	Electrode positions.
[in]	Vval	The potential values.
[in]	client.

Returns: true when successful.

Definition at line 807 of file fwd_eeg_sphere_model.cpp.

◆ fwd_eeg_spherepot_coil_vec()

int FwdEegSphereModel::fwd_eeg_spherepot_coil_vec	(	const Eigen::Vector3f &	rd,
		FwdCoilSet &	els,
		Eigen::Ref< Eigen::MatrixXf >	Vval_vec,
		void *	client )

static

fwd_multi_spherepot.c

Calculate the EEG in the sphere model using the fwdCoilSet structure MEG channels are skipped

This routine uses the acceleration with help of equivalent sources in the homogeneous sphere.

Parameters

[in]	rd	Dipole position.
[in]	els	Electrode positions.
[in]	Vval_vec	The potential values; Vval_vec[0][k] potentials given by Q = (1.0,0.0,0.0) at electrode k; Vval_vec[1][k] potentials given by Q = (0.0,1.0,0.0) at electrode k; Vval_vec[2][k] potentials given by Q = (0.0,0.0,1.0) at electrode k.
[in]	client.

Returns: true when successful.

Definition at line 634 of file fwd_eeg_sphere_model.cpp.

◆ fwd_eeg_spherepot_grad_coil()

int FwdEegSphereModel::fwd_eeg_spherepot_grad_coil	(	const Eigen::Vector3f &	rd,
		const Eigen::Vector3f &	Q,
		FwdCoilSet &	coils,
		Eigen::Ref< Eigen::VectorXf >	Vval,
		Eigen::Ref< Eigen::VectorXf >	xgrad,
		Eigen::Ref< Eigen::VectorXf >	ygrad,
		Eigen::Ref< Eigen::VectorXf >	zgrad,
		void *	client )

static

Compute potentials and spatial gradients of the potential field at coils using finite differences.

Parameters

[in]	rd	Dipole position.
[in]	Q	Dipole moment.
[in]	coils	Set of coils/electrodes.
[out]	Vval	Computed potentials (one per coil).
[out]	xgrad	Gradient with respect to x dipole coordinate.
[out]	ygrad	Gradient with respect to y dipole coordinate.
[out]	zgrad	Gradient with respect to z dipole coordinate.
[in]	client	Pointer to the FwdEegSphereModel.

Returns: OK on success, FAIL otherwise.

Definition at line 664 of file fwd_eeg_sphere_model.cpp.

◆ fwd_eeg_spherepot_vec()

bool FwdEegSphereModel::fwd_eeg_spherepot_vec	(	const Eigen::Vector3f &	rd,
		const Eigen::Matrix< float, Eigen::Dynamic, 3, Eigen::RowMajor > &	el,
		int	neeg,
		Eigen::MatrixXf &	Vval_vec,
		void *	client )

static

Compute the electric potentials in a set of electrodes in spherically Symmetric head model. This routine calculates the fields for all dipole directions.

The code is based on the formulas presented in

J.C. Moscher, R.M. Leahy, and P.S. Lewis, Matrix Kernels for Modeling of EEG and MEG Data, Los Alamos Technical Report, LA-UR-96-1993, 1996.

This routine uses the acceleration with help of equivalent sources in the homogeneous sphere.

Parameters

[in]	rd	Dipole position.
[in]	el	Electrode positions.
[in]	neeg	Number of electrodes.
[in]	Vval_vec	The potential values Vval_vec[0][k] potentials given by Q = (1.0,0.0,0.0) at electrode k; Vval_vec[1][k] potentials given by Q = (0.0,1.0,0.0) at electrode k; Vval_vec[2][k] potentials given by Q = (0.0,0.0,1.0) at electrode k.

Returns: true when successful.

Definition at line 532 of file fwd_eeg_sphere_model.cpp.

◆ fwd_setup_eeg_sphere_model()

bool FwdEegSphereModel::fwd_setup_eeg_sphere_model	(	float	rad,
		bool	fit_berg_scherg,
		int	nfit )

fwd_eeg_sphere_models.c

Setup the EEG sphere model calculations

Parameters

[in]	rad.
[in]	fit_berg_scherg	If Fit Berg Scherg should be performed.
[in]	nfit.

Returns: True when setup was successful, false otherwise.

Definition at line 835 of file fwd_eeg_sphere_model.cpp.

◆ new_fit_user()

fitUser FwdEegSphereModel::new_fit_user	(	int	nfit,
		int	nterms )

static

Allocate and initialize a fitting workspace for Berg-Scherg parameter estimation.

Parameters

[in]	nfit	Number of equivalent dipoles to fit.
[in]	nterms	Number of terms in the series expansion.

Returns: Pointer to the initialized fitting data structure.

Definition at line 186 of file fwd_eeg_sphere_model.cpp.

◆ next_legen()

void FwdEegSphereModel::next_legen	(	int	n,
		double	x,
		double &	p0,
		double &	p01,
		double &	p1,
		double &	p11 )

static

Compute the next Legendre polynomials of the first and second kind using a recursion formula. Self-initializes for n = 0 and n = 1.

Parameters

[in]	n	Order of the Legendre polynomial.
[in]	x	Evaluation point (cosine of the angle).
[out]	p0	Legendre polynomial of the first kind.
[out]	p01	Previous value of p0.
[out]	p1	Legendre polynomial of the second kind.
[out]	p11	Previous value of p1.

Definition at line 310 of file fwd_eeg_sphere_model.cpp.

◆ nlayer()

int FWDLIB::FwdEegSphereModel::nlayer ( ) const

inline

Definition at line 430 of file fwd_eeg_sphere_model.h.

◆ one_step()

double FwdEegSphereModel::one_step	(	const Eigen::VectorXd &	mu,
		const void *	user_data )

static

Objective function for the simplex optimizer: evaluate the residual sum of squares for a given set of mu values.

Parameters

[in]	mu	Distance multipliers to evaluate.
[in]	user_data	Pointer to the fitUser workspace.

Returns: Sum of squared residuals; 1.0 if any mu exceeds +/-1.

Definition at line 1007 of file fwd_eeg_sphere_model.cpp.

◆ setup_eeg_sphere_model()

FwdEegSphereModel::UPtr FwdEegSphereModel::setup_eeg_sphere_model	(	const QString &	eeg_model_file,
		QString	eeg_model_name,
		float	eeg_sphere_rad )

static

Set up the desired sphere model for EEG

Parameters

[in]	eeg_model_file	Contains the model specifications.
[in]	eeg_model_name	Name of the model to use.
[in]	eeg_sphere_rad	Outer surface radius.

Returns: the setup eeg sphere model.

Definition at line 162 of file fwd_eeg_sphere_model.cpp.

Member Data Documentation

◆ fn

Eigen::VectorXd FWDLIB::FwdEegSphereModel::fn

Coefficients saved to speed up the computations.

Definition at line 440 of file fwd_eeg_sphere_model.h.

◆ lambda

Eigen::VectorXf FWDLIB::FwdEegSphereModel::lambda

Definition at line 444 of file fwd_eeg_sphere_model.h.

◆ layers

std::vector<FwdEegSphereLayer> FWDLIB::FwdEegSphereModel::layers

An array of layers.

Definition at line 437 of file fwd_eeg_sphere_model.h.

◆ mu

Eigen::VectorXf FWDLIB::FwdEegSphereModel::mu

The Berg-Scherg equivalence parameters.

Definition at line 443 of file fwd_eeg_sphere_model.h.

◆ name

QString FWDLIB::FwdEegSphereModel::name

Textual identifier.

Definition at line 436 of file fwd_eeg_sphere_model.h.

◆ nfit

int FWDLIB::FwdEegSphereModel::nfit

How many?.

Definition at line 445 of file fwd_eeg_sphere_model.h.

◆ nterms

int FWDLIB::FwdEegSphereModel::nterms

How many?.

Definition at line 441 of file fwd_eeg_sphere_model.h.

◆ r0

Eigen::Vector3f FWDLIB::FwdEegSphereModel::r0

The origin.

Definition at line 438 of file fwd_eeg_sphere_model.h.

◆ scale_pos

int FWDLIB::FwdEegSphereModel::scale_pos

Scale the positions to the surface of the sphere?.

Definition at line 446 of file fwd_eeg_sphere_model.h.

The documentation for this class was generated from the following files:

src/libraries/fwd/fwd_eeg_sphere_model.h
src/libraries/fwd/fwd_eeg_sphere_model.cpp

Public Types

Public Member Functions

Static Public Member Functions

Public Attributes

Detailed Description

Member Typedef Documentation

◆ UPtr

Constructor & Destructor Documentation

◆ FwdEegSphereModel() [1/2]

◆ FwdEegSphereModel() [2/2]

◆ ~FwdEegSphereModel()

Member Function Documentation

◆ calc_pot_components()

◆ compose_linear_fitting_data()

◆ compute_linear_parameters()

◆ fwd_create_eeg_sphere_model()

◆ fwd_eeg_fit_berg_scherg()

◆ fwd_eeg_get_multi_sphere_model_coeff()

◆ fwd_eeg_multi_spherepot()

◆ fwd_eeg_multi_spherepot_coil1()

◆ fwd_eeg_spherepot()

◆ fwd_eeg_spherepot_coil()

◆ fwd_eeg_spherepot_coil_vec()

◆ fwd_eeg_spherepot_grad_coil()

◆ fwd_eeg_spherepot_vec()

◆ fwd_setup_eeg_sphere_model()

◆ new_fit_user()

◆ next_legen()

◆ nlayer()

◆ one_step()

◆ setup_eeg_sphere_model()

Member Data Documentation

◆ fn

◆ lambda

◆ layers

◆ mu

◆ name

◆ nfit

◆ nterms

◆ r0

◆ scale_pos